Coated article with low-e coating having low visible transmission

ABSTRACT

This invention relates to a coated article including a low-emissivity (low-E) coating. In certain example embodiments, the low-E coating is provided on a substrate (e.g., glass substrate) and includes at least first and second infrared (IR) reflecting layers (e.g., silver based layers) that are spaced apart by contact layers (e.g., NiCr based layers) and a dielectric layer of or including a material such as silicon nitride. In certain example embodiments, the coated article has a low visible transmission (e.g., no greater than 50%, more preferably no greater than about 40%, and most preferably no greater than about 39%).

This invention relates to a coated article including a low-emissivity(low-E) coating. In certain example embodiments, the low-E coating isprovided on a substrate (e.g., glass substrate) and includes at leastfirst and second infrared (IR) reflecting layers (e.g., silver basedlayers) that are spaced apart by contact layers (e.g., NiCr basedlayers) and a dielectric layer of or including a material such assilicon nitride. In certain example embodiments, the coated article hasa low visible transmission (e.g., no greater than 50%, more preferablyno greater than about 42%, and most preferably no greater than about39%). In certain example embodiments, the coated article may be heattreated (e.g., thermally tempered and/or heat bent), and is designed tobe substantially thermally stable upon heat treatment (HT) in that itsΔE* value (glass side reflective) due to HT is no greater than 4.6, andmore preferably no greater than 3.6. Coated articles according tocertain example embodiments of this invention may be used in the contextof insulating glass (IG) window units, vehicle windows, other types ofwindows, or in any other suitable application.

BACKGROUND OF THE INVENTION

Coated articles are known in the art for use in window applications suchas insulating glass (IG) window units, vehicle windows, and/or the like.It is known that in certain instances, it is desirable to heat treat(e.g., thermally temper, heat bend and/or heat strengthen) such coatedarticles for purposes of tempering, bending, or the like. Heat treatment(HT) of coated articles typically requires use of temperature(s) of atleast 580 degrees C., more preferably of at least about 600 degrees C.and still more preferably of at least 620 degrees C. Such hightemperatures (e.g., for 5-10 minutes or more) often cause coatings tobreak down and/or deteriorate or change in an unpredictable manner.Thus, it is desirable for coatings to be able to withstand such heattreatments (e.g., thermal tempering), if desired, in a predictablemanner that does not significantly damage the coating.

In certain situations, designers of coated articles strive for acombination of desirable visible transmission, desirable color, lowemissivity (or emittance), and low sheet resistance (R_(s)).Low-emissivity (low-E) and low sheet resistance characteristics permitsuch coated articles to block significant amounts of IR radiation so asto reduce for example undesirable heating of vehicle or buildinginteriors.

U.S. Pat. No. 7,521,096, incorporated herein by reference, discloses alow-E coating which uses zinc oxide (ZnO) contact layers below thesilver-based IR reflecting layers, and above the bottom silver (Ag)based IR reflecting layer uses a NiCrO_(x) contact layer followed by acenter tin oxide (SnO₂) dielectric layer. While the ZnO contact layersbelow the silver IR reflecting layers provide good structural propertiesfor the growth Of silver, the ZnO has been found to degrade thechemical, environmental and mechanical durability of the coating incertain instances. Moreover, the thick SnO₂ dielectric layer has beenfound to show micro crystallization and stress upon HT which causesrough interfaces between the SnO₂, the ZnO and the Ag, which can lead todegradation of durability and affect transmitted color.

U.S. Pat. No. 5,557,462 discloses a low-E coating with a layer stack ofSiN/NiCr/Ag/NiCr/SiN/NiCr/Ag/NiCr/SiN. However, the coated article ofthe '462 patent is designed for a high visible transmission of at least63%. Lower visible transmissions are often desirable. Moreover, aslargely explained in U.S. Pat. No. 8,173,263, coated articles of the'462 patent are not heat treatable because upon heat treatment sheetresistance (R_(s)) goes way up such as from about 3-5 to well over 10,haze tends to set in, and the glass side reflective ΔE* value isundesirable because it is over 5.0.

Accordingly, it would be desirable to provided a coated article that ischaracterized by one or more of: (i) low visible transmission, (ii) gooddurability, and (iii) thermal stability upon HT so as to realize a glassside reflective ΔE* value no greater than about 4.6, more preferably nogreater than about 3.6.

The term ΔE* (and ΔE) is well understood in the art and is reported,along with various techniques for determining it, in ASTM 2244-93 aswell as being reported in Hunter et. al., The Measurement of Appearance,2^(nd) Ed. Cptr. 9, page 162 et seq. [John Wiley & Sons, 1987]. As usedin the art, ΔE* (and ΔE) is a way of adequately expressing the change(or lack thereof) in reflectance and/or transmittance (and thus colorappearance, as well) in an article after or due to heat treatment. ΔEmay be calculated by the “ab” technique, or by the Hunter technique(designated by employing a subscript “H”). ΔE corresponds to the HunterLab L, a, b scale (or L_(h), a_(h), b_(h)). Similarly, ΔE* correspondsto the CIE LAB Scale L*, a*, b*. Both are deemed useful, and equivalentfor the purposes of this invention. For example, as reported in Hunteret. al. referenced above, the rectangular coordinate/scale technique(CIE LAB 1976) known as the L*, a*, b* scale may be used, wherein: L* is(CIE 1976) lightness units; a* is (CIE 1976) red-green units; b* is (CIE1976) yellow-blue units; and the distance ΔE* between L*_(o) a*_(o)b*_(o) and L*₁ a*₁ b*₁ is: ΔE*=[(ΔL*)²+(Δa*)²+(Δb*)²]^(1/2), where:ΔL*=L*₁−L*_(o); Δa*=a*₁−a*_(o); Δb*=b*₁−b*_(o); where the subscript “o”represents the coating (coated article) before heat treatment and thesubscript “1” represents the coating (coated article) after heattreatment; and the numbers employed (e.g., a*, b*, L*) are thosecalculated by the aforesaid (CIE LAB 1976) L*, a*, b* coordinatetechnique. When, for example, glass side reflective ΔE* values aremeasured, then glass side reflective a*, b* and L* values are used. In asimilar manner, ΔE may be calculated using the above equation for ΔE*,i.e., ΔE*=[(ΔL*)²+(Δa*)²+(Δb*)²]^(1/2)], by replacing a*, b*, L* withHunter Lab values a_(h), b_(h), L_(h). Also within the scope of thisinvention and the quantification of ΔE* are the equivalent numbers ifconverted to those calculated by any other technique employing the sameconcept of ΔE* as defined above.

BRIEF SUMMARY OF EXAMPLE EMBODIMENTS OF THE INVENTION

This invention relates to a coated article including a low-emissivity(low-E) coating. In certain example embodiments, the low-E coating isprovided on a substrate (e.g., glass substrate) and includes at leastfirst and second infrared (IR) reflecting layers (e.g., silver basedlayers) that are spaced apart by contact layers (e.g., NiCr basedlayers) and a dielectric layer of or including a material such assilicon nitride. In certain example embodiments, the coated article hasa low visible transmission (e.g., no greater than 50%, more preferablyno greater than about 42%, more preferably no greater than about 40%,and most preferably no greater than about 39%). In certain exampleembodiments, the coated article may be heat treated (e.g., thermallytempered and/or heat bent), and is designed to be substantiallythermally stable upon heat treatment (HT) in that its ΔE* value (glassside reflective) due to HT is no greater than 4.6, more preferably nogreater than 3.6. Such a low ΔE* value indicates that the coated articlehas approximately the same transmission and color characteristics asviewed by the naked eye both before and after heat treatment (e.g.,thermal tempering). Coated articles according to certain exampleembodiments of this invention may be used in the context of insulatingglass (IG) window units, vehicle windows, other types of windows, or inany other suitable application.

It is desired to provide a coated article that is characterized by one,two, or all three of: (i) low visible transmission, (ii) gooddurability, and (iii) thermal stability upon HT so as to realize a glassside reflective ΔE* value no greater than 4.6, more preferably nogreater than 3.6.

In certain example embodiments of this invention, there is provided acoated article including a coating supported by a glass substrate,comprising: first and second infrared (IR) reflecting layers comprisingsilver, the first IR reflecting layer being located closer to the glasssubstrate than is the second IR reflecting layer; a first contact layercomprising NiCr located over and directly contacting the first IRreflecting layer comprising silver; a dielectric layer comprisingsilicon nitride located over and directly contacting the first contactlayer comprising NiCr; a second contact layer comprising NiCr locatedover and directly contacting the layer comprising silicon nitride; thesecond IR reflecting layer comprising silver located over and directlycontacting the second contact layer comprising NiCr; and wherein thesecond IR reflecting layer comprising silver is at least 10 angstroms(Å) thinner than the first IR reflecting layer comprising silver, andwherein the coated article has a visible transmission of no greater than50%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a coated article according to anexample embodiment of this invention.

FIG. 2 is a cross sectional view showing the coated article of FIG. 1provided in an IG window unit according to an example embodiment of thisinvention.

FIG. 3 is a cross sectional view showing the coated article of FIG. 1provided in a laminated window unit according to an example embodimentof this invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Coated articles herein may be used in applications such as IG windowunits, laminated window units (e.g., for use in vehicle or buildingapplications), vehicle windows, monolithic architectural windows,residential windows, and/or any other suitable application that includessingle or multiple glass substrates.

In certain example embodiments of this invention, the coating includes adouble-silver stack, although this invention is not so limited in allinstances. Referring to FIG. 1 for example, in certain exampleembodiments of this invention, there is provided a coated articleincluding a coating supported by a glass substrate, the coatingcomprising: first 9 and second 19 infrared (IR) reflecting layerscomprising silver, the first IR reflecting layer 9 being located closerto the glass substrate 1 than is the second IR reflecting layer 19; afirst contact layer comprising NiCr 11 located over and directlycontacting the first IR reflecting layer comprising silver 9; adielectric layer comprising silicon nitride 14 located over and directlycontacting the first contact layer comprising NiCr 11; a second contactlayer comprising NiCr 17 located over and directly contacting the layercomprising silicon nitride 14; the second IR reflecting layer comprisingsilver 19 located over and directly contacting the second contact layercomprising NiCr 17; and wherein the second IR reflecting layercomprising silver 19 is at least 10 angstroms (Å) thinner than the firstIR reflecting layer comprising silver 9, and wherein the coated articlehas a visible transmission of no greater than 50%.

In order to increase durability, along with optics and thermalproperties, and avoid significant structural changes before and afterHT, coated articles according to certain example embodiments of thisinvention have a center dielectric layer 14 of or including siliconnitride and lower contact layers 7, 17 are based on NiCr (as opposed toZnO). It has also been found that using metallic or substantiallymetallic NiCr (possibly partly nitrided) for layer(s) 7, 11, 17 and/or21 improves chemical, mechanical and environmental durability (comparedto using ZnO lower contact layers below silver and/or highly oxided NiCrupper contact layers above silver). It has also been found thatsputter-depositing silicon nitride inclusive layer 14 in an amorphousstate, so that it is amorphous in both as-coated and HT states, helpswith overall stability of the coating. For example, 5% HCl at 65 degreesC. for one hour will remove the coating of U.S. Pat. No. 7,521,096,whereas the coating shown in FIG. 1 and the examples herein will survivethis HCl test. And in high temperature and high humidity environment,there is less damage to the coating of FIG. 1 and the examples hereinafter ten days of exposure, than to the coating of the '096 patent aftertwo days of exposure. And regarding high corrosive chemicals such asthose used for “brick wash”, corrosion resistance is such that edgedeletion need not be performed in certain example IG and laminatedembodiments. Similarly, for mechanical abrasion tests, thermal cyclingand salt fog tests, the coatings of the examples herein were found to bebetter than that of the '096 patent. Moreover, it has been found thatmaking the top Ag based IR reflecting layer 19 substantially thinnerthan the bottom Ag based IR reflecting layer 9 improves corrosionresistance and improves slightly solar performance. The coating can beused as-coated, or heat treated, due to the relatively low ΔE* valuesdiscussed herein. For example, when the coating 30 is located surface #2of an IG window unit, low glass side reflective ΔE* values due to heattreatment indicate that the coated article has approximately the sametransmission and color characteristics as viewed by the naked eye bothbefore and after heat treatment (e.g., thermal tempering), and thus canbe used either as-coated or as heat treated without significantlyaffecting optical characteristics thereof.

In certain example embodiments of this invention such as FIG. 1, heattreated or non-heat-treated coated articles having multiple IRreflecting layers (e.g., two spaced apart silver based layers) arecapable of realizing a sheet resistance (R_(s)) of less than or equal to5.0 (more preferably less than or equal to 4.0, even more preferablyless than or equal to 3.0). The terms “heat treatment” and “heattreating” as used herein mean heating the article to a temperaturesufficient to achieve thermal tempering, heat bending, and/or heatstrengthening of the glass inclusive article. This definition includes,for example, heating a coated article in an oven or furnace at atemperature of least about 580 degrees C., more preferably at leastabout 600 degrees C., for a sufficient period to allow tempering,bending, and/or heat strengthening. In certain instances, the HT may befor at least about 4 or 5 minutes. The coated article may or may not beheat treated in different embodiments of this invention.

FIG. 1 is a side cross sectional view of a coated article according toan example non-limiting embodiment of this invention. The coated articleincludes substrate 1 (e.g., clear, green, bronze, or blue-green glasssubstrate from about 1.0 to 10.0 mm thick, more preferably from about1.0 mm to 3.5 mm thick), and low-E coating (or layer system) 30 providedon the substrate 1 either directly or indirectly. The coating (or layersystem) 30 includes, for example: bottom dielectric silicon nitridelayer 3 which may be Si₃N₄, or of the Si-rich type silicon nitride forhaze reduction, or of any other suitable stoichiometry silicon nitridein different embodiments of this invention, lower contact layer 7 (whichcontacts bottom IR reflecting layer 9), first conductive and preferablymetallic or substantially metallic infrared (IR) reflecting layer 9,upper contact layer 11 (which contacts layer 9), dielectric siliconnitride based and/or inclusive layer 14, lower contact layer 17 (whichcontacts IR reflecting layer 19), second conductive and preferablymetallic or substantially metallic IR reflecting layer 19, upper contactlayer 21 (which contacts layer 19), dielectric silicon nitride layer 24which may be Si₃N₄, of the Si-rich type for haze reduction, or of anyother suitable stoichiometry silicon nitride in different embodiments ofthis invention, and overcoat layer 27 of or including a material such aszirconium oxide (e.g., ZrO₂). The “contact” layers 7, 11, 17 and 21 eachcontact an IR reflecting layer (e.g., layer based on Ag). The aforesaidlayers 3-27 make up low-E (i.e., low emissivity) coating 30 that isprovided on glass or plastic substrate 1. Layers 3-27 may besputter-deposited on the substrate 1 in certain example embodiments ofthis invention, with each layer being sputter-deposited in vacuum usingone or more targets as needed (the sputtering targets may be ceramic ormetallic). Metallic layers may be sputtered in an atmosphere containingargon gas, whereas nitrided layers may be sputtered in an atmospherecontaining a mixture of nitrogen and argon gas.

In monolithic instances, the coated article includes only one glasssubstrate 1 as illustrated in FIG. 1. However, monolithic coatedarticles herein may be used in devices such as laminated vehiclewindshields, IG window units, and the like. As for IG window units, anIG window unit may include two spaced apart glass substrates. An exampleIG window unit is illustrated and described, for example, in U.S. PatentDocument No. 2004/0005467, the disclosure of which is herebyincorporated herein by reference. FIG. 2 shows an example IG window unitincluding the coated glass substrate 1 shown in FIG. 1 coupled toanother glass substrate 2 via spacer(s), sealant(s) 40 or the like, witha gap 50 being defined therebetween. This gap 50 between the substratesin IG window unit embodiments may in certain instances be filled with agas such as argon (Ar). An example IG unit may comprise a pair of spacedapart clear glass substrates each about 3-4 mm thick, one of which iscoated with a coating 30 herein in certain example instances, where thegap 50 between the substrates may be from about 5 to 30 mm, morepreferably from about 10 to 20 mm, and most preferably about 16 mm. Incertain example instances, the low-E coating 30 may be provided on theinterior surface of either substrate facing the gap (the coating isshown on the interior major surface of substrate 1 in FIG. 2 facing thegap 50, but instead could be on the interior major surface of substrate2 facing the gap 50). Either substrate 1 or substrate 2 may be theoutermost substrate of the IG window unit at the building exterior(e.g., in FIG. 2 the substrate 1 is the substrate closest to thebuilding exterior, and the coating 30 is provided on surface #2 of theIG window unit).

FIG. 3 shows a laminated window unit including the coated glasssubstrate 1 shown in FIG. 1 coupled to another glass substrate 2 vialaminating film (e.g., PVB) 60. As shown in FIG. 3, the low-E coating 0may abut the laminating film 60 in such products.

In certain example embodiments of this invention, one, two, three, orall four of contact layers 7, 11, 17, 21 may be of or include NiCr (anysuitable ratio or Ni:Cr), and may or may not be nitrided (NiCrN_(x)). Incertain example embodiments, one, two, three or all four of these NiCrinclusive layers 7, 11, 17, 21 is substantially or entirelynon-oxidized. In certain example embodiments, one, two, three or allfour of NiCr based layers 7, 11, 17, 21 may comprise from 0-10% oxygen,more preferably from 0-5% oxygen, and most preferably from 0-2% oxygen(atomic %). In certain example embodiments, one, two, three or all fourof these layers 7, 11, 17, 21 may contain from 0-20% nitrogen, morepreferably from 1-15% nitrogen, and most preferably from about 1-12%nitrogen (atomic %). While NiCr is a preferred material for theabsorption layers 4 and 25, it is possible that other materials mayinstead or additionally be used. For example, NiCr based layers 7, 11,17 and/or 21 may or may not be doped with other material(s) such asstainless steel, Mo, or the like. It has been found that the use of NiCrbased contact layer(s) 7 and/or 17 under the silver-based IR reflectinglayer(s) 9, 19 improves durability of the coated article (compared to iflayers 7 and 17 were instead of ZnO).

Dielectric layers 3, 14, and 24 may be of or include silicon nitride incertain embodiments of this invention. Silicon nitride layers 3, 14 and24 may, among other things, improve heat-treatability of the coatedarticles and protect the other layers during optional HT, e.g., such asthermal tempering or the like. One or more of the silicon nitride oflayers 3, 14, 24 may be of the stoichiometric type (i.e., Si₃N₄), oralternatively of the Si-rich type of silicon nitride in differentembodiments of this invention. The presence of free Si in a Si-richsilicon nitride inclusive layer 3 and/or 14 may, for example, allowcertain atoms such as sodium (Na) which migrate outwardly from the glass1 during HT to be more efficiently stopped by the Si-rich siliconnitride inclusive layer(s) before they can reach silver and damage thesame. Thus, it is believed that the Si-rich Si_(x)N_(y) can reduce theamount of damage done to the silver layer(s) during HT in certainexample embodiments of this invention thereby allowing sheet resistance(R_(s)) to decrease or remain about the same in a satisfactory manner.Moreover, it is believed that the Si-rich Si_(x)N_(y) in layers 3, 14and/or 24 can reduce the amount of damage (e.g., oxidation) done to thesilver and/or NiCr during HT in certain example optional embodiments ofthis invention. In certain example embodiments, when Si-rich siliconnitride is used, the Si-rich silicon nitride layer (3, 14 and/or 24) asdeposited may be characterized by Si_(x)N_(y) layer(s), where x/y may befrom 0.76 to 1.5, more preferably from 0.8 to 1.4, still more preferablyfrom 0.82 to 1.2. Any and/or all of the silicon nitride layers discussedherein may be doped with other materials such as stainless steel oraluminum in certain example embodiments of this invention. For example,any and/or all silicon nitride layers discussed herein may optionallyinclude from about 0-15% aluminum, more preferably from about 1 to 10%aluminum, in certain example embodiments of this invention. The siliconnitride may be deposited by sputtering a target of Si or SiAl, in anatmosphere having argon and nitrogen gas, in certain embodiments of thisinvention. Small amounts of oxygen may also be provided in certaininstances in the silicon nitride layers.

Infrared (IR) reflecting layers 9 and 19 are preferably substantially orentirely metallic and/or conductive, and may comprise or consistessentially of silver (Ag), gold, or any other suitable IR reflectingmaterial. IR reflecting layers 9 and 19 help allow the coating to havelow-E and/or good solar control characteristics. The IR reflectinglayers may, however, be slightly oxidized in certain embodiments of thisinvention.

Other layer(s) below or above the illustrated coating may also beprovided. Thus, while the layer system or coating is “on” or “supportedby” substrate 1 (directly or indirectly), other layer(s) may be providedtherebetween. Thus, for example, the coating of FIG. 1 may be considered“on” and “supported by” the substrate 1 even if other layer(s) areprovided between layer 3 and substrate 1. Moreover, certain layers ofthe illustrated coating may be removed in certain embodiments, whileothers may be added between the various layers or the various layer(s)may be split with other layer(s) added between the split sections inother embodiments of this invention without departing from the overallspirit of certain embodiments of this invention.

While various thicknesses and materials may be used in layers indifferent embodiments of this invention, example thicknesses andmaterials for the respective layers on the glass substrate 1 in the FIG.1 embodiment are as follows, from the glass substrate outwardly:

Example Materials/Thicknesses; FIG. 1 Embodiment

Layer Preferred More Glass (1-10 mm thick) Range ({acute over (Å)})Preferred ({acute over (Å)}) Example (Å) Si_(x)N_(y) (layer 3) 100-500{acute over (Å)} 250-450 {acute over (Å)} 339 Å NiCr or NiCrN (layer 7)10-45 {acute over (Å)} 15-30 {acute over (Å)} 18-25 Å Ag (layer 9)90-165 {acute over (Å)} 110-145 {acute over (Å)} 128 Å NiCr or NiCrN(layer 11) 10-45 {acute over (Å)} 15-30 {acute over (Å)} 18-25 ÅSi_(x)N_(y) (layer 14) 300-1400 {acute over (Å)} 400-1200 {acute over(Å)} 700-990 Å NiCr or NiCrN (layer 17) 5-22 {acute over (Å)} 6-14{acute over (Å)} 7-11 Å Ag (layer 19) 50-115 {acute over (Å)} 60-95{acute over (Å)} 79 Å NiCr or NiCrN (layer 21) 8-30 {acute over (Å)}10-20 {acute over (Å)} 11-18 Å Si₃N₄ (layer 24) 100-500 {acute over (Å)}150-290 {acute over (Å)} 200-260 Å ZrO₂ (layer 27) 25-150 {acute over(Å)} 35-80 {acute over (Å)} 50 Å

In certain example embodiments of this invention, coated articles hereinmay have the following optical and solar characteristics set forth inTable 2 when measured monolithically (before and/or after optional HT).The sheet resistances (R_(s)) herein take into account all IR reflectinglayers (e.g., silver layers 9, 19).

Optical/Solar Characteristics (Monolithic)

Characteristic General More Preferred Most Preferred R_(s) (ohms/sq.):<=5.0 <=4.0 <=3.0 E_(n): <=0.08 <=0.05 <=0.04 T_(vis) (Ill. C 2°):10-60% 20-42% 27-39%

In certain example laminated embodiments of this invention, coatedarticles herein which have been optionally heat treated to an extentsufficient for tempering, and which have been coupled to another glasssubstrate to form an IG unit, may have the above recited Optical/Solarcharacteristics in a structure as shown in FIG. 2 (e.g., where the twoglass sheets are 4 mm thick and 6 mm thick respectively of clear glasswith a 16 mm gap therebetween filled with 90/10 argon/air). Such IGwindow units may have a visible transmission of from about 20-40% incertain example embodiments of this invention. Alternatively, coatedarticles herein which have been optionally heat treated to an extentsufficient for tempering, and which have been coupled to another glasssubstrate via laminating material such as PVB 60 to form a laminatedwindow unit, may have the above recited Optical/Solar characteristics ina structure as shown in FIG. 3 (i.e., the FIG. 3 laminated structure mayhave the Optical/Solar characteristics recited above).

The following examples are provided for purposes of example only, andare not intended to be limiting unless specifically claimed.

EXAMPLES 1-3

The following Examples 1-3 were made via sputtering coatings on 4 mmthick clear/transparent glass substrates so as to have approximately thelayer stacks set forth below. The layer thicknesses below for theexamples are in units of angstroms ({acute over (Å)}), from the glasssubstrate moving outwardly.

Layer Example 1 Example 2 Example 3 Si_(x)N_(y) (layer 3) 339 {acuteover (Å)} 343 Å 326 Å NiCr (layer 7) 20 {acute over (Å)} 40 {acute over(Å)} 14 Å Ag (layer 9) 128 {acute over (Å)} 122 {acute over (Å)} 148 ÅNiCr (layer 11) 22 {acute over (Å)} 22 {acute over (Å)} 22 Å Si_(x)N_(y)(layer 14) 880 {acute over (Å)} 958 {acute over (Å)} 960 Å NiCr (layer17) 8 {acute over (Å)} 8 {acute over (Å)} 8 Å Ag (layer 19) 79 {acuteover (Å)} 79 {acute over (Å)} 79 Å NiCr (layer 21) 14 {acute over (Å)}14 {acute over (Å)} 14 Å Si₃N₄ (layer 24) 235 {acute over (Å)} 268{acute over (Å)} 238 Å ZrO₂ (layer 27) 50 {acute over (Å)} 50 {acuteover (Å)} 50 Å

Set forth below are the optical characteristics of Examples 1-3 measuredin a laminated structure with two glass substrates as shown in FIG. 3.All values measured in the table immediately below are pre-HT, exceptthat the ΔE* values were due to 11T.

Monolithic

Characteristic Ex. 1 Ex. 2 Ex. 3 T_(vis) (or TY)(Ill. C 2°): 39.3% 33.7%37.1% a*_(t) (Ill. C 2°): −5.5 −5.5 −4.3 b*_(t) (Ill. C 2°): −1.3 +2.8+2.8 R_(f)Y (Ill. C, 2 deg.): 13.4% 18.9% 22.5% a*_(f) (Ill. C, 2°):−9.5 −15.5  −18.1  b*_(f) (Ill. C, 2°): −23.3  −17.2  −11.0  R_(g)Y(Ill. C, 2 deg.): 18.3 22.6% 26.0% a*_(g) (Ill. C, 2°): +1.1 −4.4 −4.0b*_(g) (Ill. C, 2°): −8.6 −4.7 −5.4 ΔE* (transmissive):  2.8  2.6  2.7ΔE* (glass side refl.):  4.4  4.3  3.6

It can be seen from the above the examples above that the coatedarticles measured monolithically had desirable visible transmission(e.g., in the range of from about 20-42% measured monolithically), andhad fairly neutral glass side reflective color. In particular, a*_(g)(glass side reflective a* color) was in a desirable range of from about−5 to +3, and b*_(g) (glass side reflective b* color) was in a desirablerange of from about −10 to +2. These are desirable characteristics,especially when the coated article is to be put in an IG window unit asshown in FIG. 2 or in a laminated window unit as shown in FIG. 3.

Set forth below are the optical characteristics of IG window unitsincluding the coated articles of Examples 1-3, namely when the coatedarticles are located in IG window units as shown in FIG. 2 (on surface#2 of the IG unit, so that glass side reflective values are indicativeof from the outside).

IG Unit

Characteristic Ex. 1 Ex. 2 Ex. 3 T_(vis) (or TY)(Ill. C 2°): 33.4% 29.5%35.1% a*_(t) (Ill. C 2°): −1.05 −1.58  −0.8  b*_(t) (Ill. C 2°): −7.83−7.3  −7.13 R_(f)Y (Ill. C, 2 deg.): 24.7% 29.1% 32.7% a*_(f) (Ill. C,2°): −17.97  −18.3   −17.42  b*_(f) (Ill. C, 2°): −2.75 8.19 12.65R_(g)Y (Ill. C, 2 deg.):   22% 23.3%   29% a*_(g) (Ill. C, 2°): −2.660.98 −2.48 b*_(g) (Ill. C, 2°):  8.12 5.01  8.35

Set forth below are the optical characteristics of laminated windowunits including the coated articles of Examples 1-3, namely when thecoated articles are located in laminated window units as shown in FIG. 3(on surface #2 of the unit, so that glass side reflective values areindicative of from the outside).

Laminated Window Unit

Characteristic Ex. 1 Ex. 2 Ex. 3 T_(vis) (or TY)(Ill. C 2°): 38.5% 33.7%40.5% a*_(t) (Ill. C 2°): −6.15 −5.48 −3.9  b*_(t) (Ill. C 2°): −1.42 2.73  2.72 R_(f)Y (Ill. C, 2 deg.): 13.2% 18.8% 22.2% a*_(f) (Ill. C,2°): −9.84 −15.61  −17.57  b*_(f) (Ill. C, 2°): −22.98  −17.14  −8.74R_(g)Y (Ill. C, 2 deg.):   18% 22.6% 25.4% a*_(g) (Ill. C, 2°):  0.62−4.34 −3.66 b*_(g) (Ill. C, 2°): −8.49 −4.64 −7.41

In certain example embodiments of this invention, there is provided acoated article including a coating supported by a glass substrate, thecoating comprising: first 9 and second 19 infrared (IR) reflectinglayers comprising silver, the first IR reflecting layer 9 being locatedcloser to the glass substrate 1 than is the second IR reflecting layer19; a first contact layer comprising NiCr 11 located over and directlycontacting the first IR reflecting layer comprising silver 9; adielectric layer comprising silicon nitride 14 located over and directlycontacting the first contact layer comprising NiCr 11; a second contactlayer comprising NiCr 17 located over and directly contacting the layercomprising silicon nitride 14; the second IR reflecting layer comprisingsilver 19 located over and directly contacting the second contact layercomprising NiCr 17; and wherein the second IR reflecting layercomprising silver 19 is at least 10 angstroms (Å) thinner than the firstIR reflecting layer comprising silver 9, and wherein the coated articlehas a visible transmission of no greater than 50% (e.g., measuredmonolithically and/or in a laminated window structure).

In the coated article of the immediately preceding paragraph, the firstcontact layer comprising NiCr may be from about 10-40 Å thick, morepreferably from about 15-30 Å thick, and most preferably from about18-25 Å thick.

In the coated article of any of the preceding two paragraphs, said firstcontact layer comprising NiCr may be from 8-22 Å thicker than the secondcontact layer comprising NiCr, more preferably said first contact layercomprising NiCr may be from 10-18 Å thicker than the second contactlayer comprising NiCr.

In the coated article of any of the preceding three paragraphs, thesecond contact layer comprising NiCr may be from about 5-22 Å thick,more preferably from about 6-14 Å thick, and most preferably from about7-11 Å thick.

In the coated article of any of the preceding four paragraphs, thesecond IR reflecting layer comprising silver may be at least 20angstroms (Å) thinner (more preferably at least 40 angstroms thinner)than the first IR reflecting layer comprising silver.

In the coated article of any of the preceding five paragraphs, thedielectric layer comprising silicon nitride 14 may be amorphous.

In the coated article of any of the preceding six paragraphs, the firstcontact layer comprising NiCr and/or the second contact layer comprisingNiCr may be substantially metallic or metallic and contain no more thanabout 5% (atomic %) oxygen.

In the coated article of any of the preceding seven paragraphs, saidfirst and/or second contact layer may further contain nitrogen (e.g.,from about 1-10%, atomic %, nitrogen).

In the coated article of any of the preceding eight paragraphs, saidcoated article may have a visible transmission of from about 20-40%(more preferably from about 27-39%) measured monolithically.

The coated article of any of the preceding nine paragraphs may or maynot be heat treated (e.g., thermally tempered). When heat treated, thecoated article may have a glass side reflective ΔE* value of no greaterthan 4.6 (more preferably no greater than 3.6, and possibly from 3.0 to4.6) due to the heat treatment.

In the coated article of any of the preceding ten paragraphs, thecoating may further include another dielectric layer 24 comprisingsilicon nitride located over at least the second IR reflecting layer 19.The another dielectric layer 24 comprising silicon nitride may be from150-290 Å thick. An overcoat comprising zirconium oxide 27 may belocated over and directly contacting the another dielectric layercomprising silicon nitride 24.

In the coated article of any of the preceding eleven paragraphs, thecoating may further include a bottom layer comprising silicon nitride 3located on and directly contacting the glass substrate 1, and anothercontact layer comprising NiCr 7 located between and directly contactingthe bottom layer comprising silicon nitride 3 and the first IRreflecting layer comprising silver 9.

In the coated article of any of the preceding twelve paragraphs, thefirst IR reflecting layer comprising silver may be from 110-145 Å thick.

In the coated article of any of the preceding thirteen paragraphs, thesecond IR reflecting layer comprising silver may be from 60-95 Å thick.

In the coated article of any of the preceding fourteen paragraphs, thecoating may have a sheet resistance of less than or equal to 4.0ohms/square.

The coated article of any of the preceding fifteen paragraphs, when heattreated, may have a transmissive ΔE* value of from 2.0 to 3.2.

The coated article of any of the preceding sixteen paragraphs may beprovided in an IG window unit, or in a laminated window unit in whichthe coated substrate is laminated to another glass substrate.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A coated article including a coating supported by a glass substrate,the coating comprising: first and second infrared (IR) reflecting layerscomprising silver, the first IR reflecting layer being located closer tothe glass substrate than is the second IR reflecting layer; a firstcontact layer comprising NiCr located over and directly contacting thefirst IR reflecting layer comprising silver; a dielectric layercomprising silicon nitride located over and directly contacting thefirst contact layer comprising NiCr; a second contact layer comprisingNiCr located over and directly contacting the layer comprising siliconnitride; the second IR reflecting layer comprising silver located overand directly contacting the second contact layer comprising NiCr; andwherein the second 1R reflecting layer comprising silver is at least 10angstroms (Å) thinner than the first IR reflecting layer comprisingsilver, and wherein the coated article has a visible transmission of nogreater than 50%.
 2. The coated article of claim 1, wherein the firstcontact layer comprising NiCr is from about 15-30 Å thick.
 3. The coatedarticle of claim 1, wherein said first contact layer comprising NiCr isfrom 8-22 Å thicker than the second contact layer comprising NiCr. 4.The coated article of claim 1, wherein said first contact layercomprising NiCr is from 10-18 Å thicker than the second contact layercomprising NiCr.
 5. The coated article of claim 1, wherein the secondcontact layer comprising NiCr is from about 6-14 Å thick.
 6. The coatedarticle of claim 1, wherein the second IR reflecting layer comprisingsilver is at least 20 angstroms (Å) thinner than the first IR reflectinglayer comprising silver.
 7. The coated article of claim 1, wherein thesecond IR reflecting layer comprising silver is at least 40 angstroms(Å) thinner than the first IR reflecting layer comprising silver.
 8. Thecoated article of claim 1, wherein the dielectric layer comprisingsilicon nitride is amorphous.
 9. The coated article of claim 1, whereinthe first contact layer comprising NiCr is substantially metallic ormetallic and contains no more than about 5% (atomic %) oxygen.
 10. Thecoated article of claim 1, wherein the second contact layer comprisingNiCr is substantially metallic or metallic and contains no more thanabout 5% (atomic %) oxygen.
 11. The coated article of claim 1, whereinsaid first and/or second contact layer further contains nitrogen. 12.The coated article of claim 1, wherein said coated article has a visibletransmission of from about 20-42% measured monolithically.
 13. Thecoated article of claim 1, wherein the coated article is thermallytempered.
 14. The coated article of claim 1, wherein the coated articleis not heat treated.
 15. The coated article of claim 1, wherein thecoated article is heat treated and has a glass side reflective ΔE* valueof no greater than 4.6 due to the heat treatment.
 16. The coated articleof claim 1, wherein the coated article is heat treated and has a glassside reflective ΔE* value of no greater than 3.6 due to the heattreatment.
 17. The coated article of claim 1, wherein the coated articleis heat treated and has a glass side reflective ΔE* value of from 3.0 to4.6 due to the heat treatment.
 18. The coated article of claim 1,wherein the coating further comprises another dielectric layercomprising silicon nitride located over at least the second IRreflecting layer.
 19. The coated article of claim 18, wherein saidanother dielectric layer comprising silicon nitride is from 150-290 Åthick.
 20. The coated article of claim 18, wherein the coating furthercomprises an overcoat comprising zirconium oxide located over anddirectly contacting the another dielectric layer comprising siliconnitride.
 21. The coated article of claim 1, wherein the coating furthercomprising a bottom layer comprising silicon nitride located on anddirectly contacting the glass substrate, and another contact layercomprising NiCr located between and directly contacting the bottom layercomprising silicon nitride and the first IR reflecting layer comprisingsilver.
 22. The coated article of claim 1, wherein the first IRreflecting layer comprising silver is from 110-145 Å thick, and thesecond IR reflecting layer comprising silver is from 60-95 Å thick. 23.The coated article of claim 1, wherein the coating has a sheetresistance (R_(s)) of less than or equal to 4.0 ohms/square.
 24. Alaminated window comprising the coated article of claim 1 laminated toanother substrate.
 25. A coated article including a coating supported bya glass substrate, comprising: first and second infrared (IR) reflectinglayers, the first IR reflecting layer being located closer to the glasssubstrate than is the second IR reflecting layer; a first substantiallymetallic contact layer comprising NiCr located over and directlycontacting the first IR reflecting layer, the first substantiallymetallic contact layer comprising NiCr being from about 15-30 Å thick; adielectric layer comprising silicon nitride located over and directlycontacting the first contact layer comprising NiCr; a secondsubstantially metallic contact layer comprising NiCr located over anddirectly contacting the layer comprising silicon nitride; the second IRreflecting layer located over and directly contacting the second contactlayer comprising NiCr; and wherein the second IR reflecting layercomprising silver is at least 10 angstroms (Å) thinner than the first IRreflecting layer comprising silver.
 26. The coated article of claim 25,wherein said first contact layer comprising NiCr is from 8-22 Å thickerthan the second contact layer comprising NiCr.
 27. The coated article ofclaim 25, wherein the second IR reflecting layer comprising silver is atleast 40 angstroms (Å) thinner than the first IR reflecting layercomprising silver.
 28. The coated article of claim 25, wherein saidcoated article has a visible transmission of from about 20-42% measuredmonolithically.
 29. The coated article of claim 25, wherein the coatedarticle is heat treated and has a glass side reflective ΔE* value of nogreater than 4.6 due to the heat treatment.
 30. A method of making acoated article including a coating supported by a glass substrate, themethod comprising: sputter-depositing first and second infrared (IR)reflecting layers comprising silver, the first IR reflecting layer beinglocated closer to the glass substrate than is the second IR reflectinglayer; sputter-depositing a first contact layer comprising NiCr locatedover and directly contacting the first IR reflecting layer comprisingsilver; sputter-depositing a dielectric layer comprising silicon nitridelocated over and directly contacting the first contact layer comprisingNiCr; sputter-depositing a second contact layer comprising NiCr locatedover and directly contacting the layer comprising silicon nitride, thesecond IR reflecting layer comprising silver located over and directlycontacting the second contact layer comprising NiCr; and wherein thesecond IR reflecting layer comprising silver is at least 10 angstroms(Å) thinner than the first IR reflecting layer comprising silver, andwherein the coated article has a visible transmission of no greater than50% measured monolithically.